生物变异的方向不是由变异决定的，是由环境来决定的。
参考答案：对
________ is known to everybody, Taiwan is a part of China. We must unify it.
A．It
B．As
C．Which
D．What
YD5121-2010《长途通信光缆线路工程验收规范》规定：硅芯管道普通土、硬土埋深应≥（）M.
A.0.8
B.1
C.1.2
D.1.3
